Launch Webviews as incognito

[Hyphrio]

Is your feature request related to a problem? Please describe.
For browser based OAuth where you cannot guarantee the existence of a web browser but can guarantee the existence of a WebView, having an option to launch a webview as incognito would be useful.

Would you want to assign yourself to implement this feature?

• Yes
• No

Other (I did a PoC for WebView2)

Additional context
On Windows, it could be done by modifying InnerWebView::create_controller to something like this:

  fn create_controller(
    hwnd: HWND,
    env: &ICoreWebView2Environment,
    incognito: bool
  ) -> webview2_com::Result<ICoreWebView2Controller> {
    let (tx, rx) = mpsc::channel();
    let env = env.clone().cast::<ICoreWebView2Environment10>()?;
    let controller_opts = unsafe {env.CreateCoreWebView2ControllerOptions()?};

    unsafe {controller_opts.SetIsInPrivateModeEnabled(incognito)?}

    CreateCoreWebView2ControllerCompletedHandler::wait_for_async_operation(
      Box::new(move |handler| unsafe {
        env
          .CreateCoreWebView2ControllerWithOptions(hwnd, &controller_opts, &handler)
          .map_err(webview2_com::Error::WindowsError)
      }),
      Box::new(move |error_code, controller| {
        error_code?;
        tx.send(controller.ok_or_else(|| windows::core::Error::from(E_POINTER)))
          .expect("send over mpsc channel");
        Ok(())
      }),
    )?;

    rx.recv()
      .map_err(|_| webview2_com::Error::SendError)?
      .map_err(webview2_com::Error::WindowsError)
  }

It would be needed to cast env to ICoreWebView2Environment10 first as ICoreWebView2Environment wouldn't have CreateCoreWebView2ControllerWithOptions.

[wusyong]

webkit2gtk can enable it via SettingsExt trait.

[Hyphrio]

Any idea for macOS/iOS and Android? I do have both Windows and WebKitGTK both implemented now (but I did have to use is_ephemeral on WebViewBuilder rather than enable_private_browsing to make the behavior more consistent like on Windows)